Composition and method for treating inflammation of the skin

ABSTRACT

THIS INVENTION RELATES TO A METHOD OF TREATING SKIN INJURIES INVOLVING INFLAMMATION OF TISSUES, SUCH AS BURNS, VARICOSE ULCERS, AND DECUBITUS ULCERS (BEDSORES), AND TO A THERAPEUTIC COMPOSITION FOR CARRYING OUT SUCH TREATMENT. FURTHERMORE THE INVENTION RELATES TO A DRESSING INCORPORATING THE THERAPEUTIC COMPOSITION, AND TO METHOD OF PREPARING THE COMPOSITION AND THE DRESSING. MORE PARTICULARLY THE INVENTION IS CONCERNED WITH A METHOD AND A COMPOSITION AND DRESSING FOR TREATING SKIN INJURIES, ESPECIALLY BURN WOUNDS, BY CONTROLLING THE EVAPORATION OF FLUID FROM THE INJURED AREA AND BY REGULATING THE TEMPERATURE OF THE INJURED AREA, SO AS TO MAINTAIN THE MICRO-CIRCULATION AND TO EXPEDITE HEALING.

A ril 25, 1912 H. F. KAMP 3,658,984

COMPOSITION AND METHOD FOR TREATING INFLAMMATION OF THE SKIN Fil ed Jan. 13, 1967 Bur/2 surface exposed W/zh dress/by /V0/'//70/ Sk/fl Inven HERMAN FERDINAND KAMP Byj bfg Attorney:

United States Patent O 3,658,984 COMPOSITION AND METHOD FOR TREATING INFLAMMATION OF THE SKIN Herman F. Kamp, 438 Farenden St., Arcadia, Pretoria, Transvaal, Republic of South Africa Filed Jan. 13, 1967, Ser. No. 609,041 Claims priority, application Republic of South Africa, Jan. 18, 1966, 66/322 Int. Cl. A61f 13/00; A611 15/03 US. Cl. 424-28 3 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a method of treating skin injuries involving inflammation of tissues, such as burns, varicose ulcers, and decubitus ulcers (bedsores), and to a therapeutic composition for carrying out such treatment. Furthermore the invention relates to a dressing incorporating the therapeutic composition, and to a method of preparing the composition and the dressing.

More particularly the invention is concerned with a method and a composition and dressing for treating skin injuries, especially burn wounds, by controlling the evaporation of fluid from the injured area and by regulating the temperature of the injured area, so as to maintain the micro-circulation and to expedite healing.

BACKGROUND OF THE INVENTION Field of the invention The invention accordingly pertains to the treatment of inflammatory conditions of the dermis and subdermis, following upon injury such as by heat or mechanical means. To this end the invention provides a dressing which in practice exhibits a therapeutic effect and favourably influences the inflammatory process by favourably affecting the temperature of and the fluid loss from the inflamed area and so maintain the micro-circulation.

Description of the prior art Hitherto, burn wounds and other skin injuries involving inflammation of tissues have normally been treated either by the so-called exposure method, or by means of an absorptive dressing.

In the exposure method, the burn wound is left open, without any covering, dressing or bandage, in order to permit free evaporation of fluid so as to dry the wound area. This method possesses a number of disadvantages. In the first place, it has been found that drying delays epithelisation, and in full thickness burns the delay before separation and removal of the eschar frequently allows secondary infection to occur. It has been stated that the increasing incidence of gram-negative bacterial infections is a direct result of the inability to remove devitalised burn tissue safely and early. Below an eschar of almost normal external appearance complete destruction of subdermal aureolar tissue and blood vessels has been found. Furthermore, it has been shown that extensive fluid loss can occur from an apparently dry eschar, and the heat 3,658,984 Patented Apr. 25, 1972 taken up by evaporation accounts in part for the excessive caloric expenditure of seriously burned patients.

The treatment by means of absorptive dressings has the disadvantage that it tends to promote infection and increase wound depth. Furthermore it has been found that extensive fluid loss takes place from a dressed burn wound, with the attendant heat losses.

-In the treatment of burn Wounds, it is important to differentiate between the two distinct phases in burn wound pathology. The first concerns the phase of rapid and copious fluid loss which, unless augmented by oral supply, may prove fatal. It is not generally realised that fluid loss from a l5-2 0% dermal burn may be as large as from a full thickness burn of much larger area where the vessels, which leak in a dermal burn, have been destroyed. As most burns can be expected to be of mixed depth of injury, it is important to have a single dressing and a method of treatment for all areas concerned.

The second phase concerns the problem of insensible fluid loss. It has been shown that large fluid losses take place through apparently dry crusts and eschars. Owing to lack of blood supply under crusts or eschars or under conventional dressings, infection often sets in which increases the depth of injury and extends morbidity. It is, therefore, of importance to have a method of treatment and a dressing which exerts a beneficial therapeutic effect while providing the necessary protection.

SUMMARY OF THE INVENTION According to the invention, a method of treating skin injuries in which inflammation of tissue is involved, in cludes the steps of cooling the injured area to a temperature lower than the normal skin temperature, progressively permitting the temperature to increase to a value in the vicinity of the normal skin temperature, and repeating this procedure.

The higher temperature may conveniently be maintained for a substantial period of time, conveniently for about twenty to twenty-four hours. The progressive increase of the temperature may be effected during a period of between about one to four hours. Thus a complete cycle of cooling and increasing the temperature may be carried out every twenty-four hours.

The coolest temperature may conveniently be between about 10 to 30 F. below the normal skin temperature. This temperature will in practice depend upon the nature of the injury being treated. Thus when a burn is treated by this method, and when the injury shows signs of inflammation, the temperature will normally be controlled at a lower value in the initial stage than in other cases.

According to a further feature of the invention, the method of treating skin injuries involving inflammation of tissues, includes the further step of controlling the evaporation of fluid from the injured area. Fluid loss by evaporation through burn injured skin is excessive and should preferably be controlled to allow only a certain degree of evaporation, such as for example a 20% evaporation, so as to avoid over-cooling of the injured area by excessive heat loss during fluid evaporation, but at the same time to prevent fluid from accumulating in the injured area.

The practical success of the method according to the invention, may be explained and justified in the light of sound medical and scientific facts. The effects of the method will now be analysed in detail with reference to the local treatment of burns. It should be understood, however, that the applicant does not intend to be bound by any theoretical explanation advanced.

BRIEF DESCRIPTION OF THE DRAWING The accompanying drawing is a graphical representation of the fluid loss from a burn wound.

DESCRIPTION OF THE PREFERRED EMBODIMENT It is known that in a burn wound, a progressive involvement of tissues and blood vessels only partially or not at all injured in the initial trauma, is encountered. Burn wound healing is impossible without prior breakdown and removal of irreversibly damaged tissues. However, this breakdown or autolysis must be controlled, to prevent uninjured, or only slightly injured cells from being adversely affected or broken down, and also to prevent unnecessary damage to small blood vessels and capillary tissue and to ensure conservation of superficial subcutaneous blood vessels and aerolar tissue, fat, and granulation tissue. The initial cooling of the injured area prevents too rapid cell breakdown and the consequent damage or destruction of uninjured tissue. However, autolysis or cell breakdown requires the aid of blood borne factors, systematic enzymes and autolysates, the latter being provided in part by breakdown products of the cells. These agents appear to require temperatures within the range of about 98 to 100 F. to become active. Therefore, the control of temperature within this range, in accordance with the invention, ensures a suitable temperature for the activation of these fatcors. The alternate cooling and heating consequently ensures that cell breakdown or autolysis does take place, but prevents excessive breakdown or autolysis, which might damage capillary and other uninjured tissue.

Furthermore, it is essential that sufficient oxygen is supplied to the injured area, and that breakdown products are removed from this area. Both these functions are normally carried out by the capillaries and small blood vessels, especially the venules, and in order to ensure that these functions are carried out eflectively, this circulation has to be maintained. Once capillary blocking and blockmg of small vessels occur through stasis, it is evident that these functions will be greatly impaired, and this could cause a serious problem in the healing of the injury.

The main problem presented by the condition of stasis is found in the venous portion of the microcirculation bed, where the intravascular pressure has increased due to a concentration of solutes and red blood cells, while pressure in the extravascular tissue has been reduced through excessive fluid loss from the blood into this tissue. It is evident that this condition will seriously impair the blood circulation, resulting in ineffective functioning of the microcirculatory system. In accordance with the invention it is proposed to solve this problem by bringing about an adrenaline-like action by the cooling of the injured area, followed by heating of the injured area, it having been found that the systemic or local administration of a suitable drug is impractical and harmful. During the cooling step of the method according to the invention, the arterioles and metarterioles on the arterial side will contract, the precapillary sphincters will close, and the arteriolar portion of the capillaries will show a degree of contraction. On the venous side the capillaries, preferential channels, and 'venules will also contract. Thereby no more concentrated blood enter the capillary bed, while the concentrated blood within the 'venous portion will be forced by the contraction of the venous portion into the general circulation.

The contraction of the arteries will, by way of a further result, control the amount of fluid carried to and away from the injured area, so that oedema will be reduced.

The gradual increase of the temperature in accordance with the invention, causes the arterioles and venules to dilate again, so that blood will again enter the capillary bed. In this manner micro-circulation is maintained, together with the various advantages attached thereto.

According to the research carried out since 1943, and more recently (1956, 1962 and 1963) in connection with the treatment of burn wounds, fluid loss through skin damaged by heat is excessive. In fact, it was found that the fluid loss increased to as much as 10 times the normal rate. It has also been shown that the property of controlling fluid loss through normal skin resides in the outermost horny layer of skin. This layer only serves as a matrix, framework, or lattice for holding the lipo-protein complexes which have been proved to be the essential factor in fluid control. The suggested mechanism involved depends upon the relationship between the lattice structure of the cornium, the water molecules, and the lipoprotein complexes, which act in combination to effect the fluid control.

In almost all burn wounds, this horny layer and its contents are destroyed, resulting in the loss of large amounts of fluid, the evaporation of which results in great heat losses from the skin. An important result of this is that the excessive heat loss after the initial heat of inflammation has subsided, cools the skin to temperature levels too low for the normal breakdown process of cells to proceed, and consequently the dead skin of full thickness burns remains adherent for many weeks. This forms a suitable breeding ground for certain types of bacteria which have lately been shown to predominate as the chief cause of bloodstream invasion and death. A great need, therefore, exists for a method to control fluid loss from the surface of a burn wound at any stage prior to healing or grafting.

As already indicated, it is important to differentiate between the two distinct phases in burn wound pathology, as far as fluid loss is concerned. During the first phase, which endures roughly during the first 48 hours after the initial trauma, large fluid losses take place as a result of injury and dilation of the vessels in a dermal burn (second degree). In a full thickness (third degree) burn, fluid loss is reduced, since the vessels are destroyed to such an extent as to have the effect of closing the wound.

During the second phase, the blood vessels in a dermal burn are blocked with red cells, due to the large serum and fluid losses during the first phase. So-called insensible fluid loss now takes place from open vessels in the peripheral area of the wound and from other tissues possessing viable blood vessels. The fluid permeates and perfuses through the damaged tissues to the surface, where evaporation takes place. In a full thickness burn, fluid is withdrawn from the damaged tissues and vessels by capillary action by the dry, friable denatured protein material of the heat destroyed dermis. This withdrawal of fluid has been found to be in excess to that lost from a dermal burn by perfusion.

The invention provides a therapeutic composition for treating skin injuries, and particularly burn wounds, by the method described above. Thus, according to the invention, there is provided a therapeutic composition which includes a mixture of mineral components comprising South African bentonite kaolinite, and South African illite, which mixture is rendered into paste form by the addition of a liquid mixture comprising water and glycerine. South African bentonite, kaolinite, and South African illite are the components having the mineralogical compositions set out in Table 1 herein.

More particularly, the therapeutic composition may in clude a mixture of mineral components comprising about 25 to 38% by weight of South African bentonite, about 30 to 50% by weight of kaolinite, and about 18 to 30% by weight of South African illite, which mixture is rendered into paste-form by the addition of a substantially equal weight of a liquid mixture comprising about 8 to 10 parts by Weight of water, and about 4 to 2 parts by weight of glycerine.

One preferred mixture of mineral components in accordance with the invention, includes about 4 parts by weight of South African bentonite, about 5 parts by weight of kaolinite, and about 3 parts by Weight of South African illite, and the liquid mixture comprises about 9 parts by weight of water and about 3 parts by weight of glycerine.

By way of explanation, the following terms when used in the specification will have the following meanings:

Kaolinite: this is a crystalline mineral of the two layer type (sheet structures composed of units of one layer of silica tetrahedrons and one layer of alumina octahedrons) which is equidimensional.

South African bentonite: this is crystalline clay mineral of the three layer type (sheet structures are composed of two layers of silica tetrahedrons and one central dioctahedral or trioctahedral layer) having an expanding lattice.

South African illite: this is a crystalline clay mineral of the three layer type (sheet structures are composed of two layers of silica tetrahedrons and one central di: octahedral or trioctahedral layer) with a nonexpanding lattice.

The composition may contain as a further ingredient a quantity of starch. The starch serves as a binder and improves the physical properties of the composition. The starch may be incorporated in a quantity of between /2- 2% based on the Weight of the liquid components of the composition, preferably about 1%.

Furthermore, the composition may advantageously include an anti-fungal agent. A suitable anti-fungal agent is methyl parahydroxybenzoate, for example in the form of the material available under the trade name Nipogen M. The anti-fungal agent may be incorporated in a quantity of between about 0.04-0.06 part by weight, based on the total weight of the composition. Preferably about 0.05 part by weight of anti-fungal agent is used.

In a particular example, a composition according to the invention may include the following ingredients in the following proportions:

Proportion (parts Ingredient (solids): by weight) Kaolin 5 Bentonite 4 Illite 3 Starch-1% of liquid weight.

Nipogen M 0.05

Liquid:

Water 8 Glycerine 3 Heat flow measurements have proved the ability of the composition of this invention, when applied as a dressing, to control fluid loss by the fact that for the greater portion of its contact with the wound it maintains the temperature of the wound to approximately normal skin temperature, by controlling the evaporation of fluids through it. This has the advantage of maintaining blood circulation in the wound; yet it prevents excessive heat formation in the wound by proved evaporation of a percentage of body fluids.

Experiments have been carried out to illustrate the capacity of the composition according to the invention to control fluid loss from a skin injury such as a burn wound, in both the aforementioned first and second phases of the burn wound treatment.

In order to simulate the fluid loss mechanism during the first phase, specimens of excised human, monkey and pig skin were defatted to remove the lipo-protein complexes and to render the skin specimens leaky. Dressings of the composition according to the invention were applied to the treated skin specimens, and the transpiration rate through the specimens plus dressings was measured. It was found that the dressing produced a marked decrease in the transpiration rate, as compared to that of the defatted skin but without the dressing. In fact, the transpiration rate was reduced to about 3-5% of its former value.

In order to determine the insensible fluid loss during the second phase, readings were taken on a microhygrometer adapted to record the difference in humidity between the atmosphere and the air coming from an isolated test area on the surface of an apparently dry burn eschar. Readings were taken with the eschar uncovered, and with the eschar covered by a dressing of the composition according to the invention. The readings were compared to those taken of normal uninjured skin. The results are indicated graphically in the accompanying drawing, in which hygrometer readings are plotted against time (in days).

It was found that the composition according to the invention, is capable of reducing the fluid loss through injured skin by about About 20% evaporation is allowed through the dressing. This has been shown to be essential for the control of temperature within the range required for the breakdown of damaged cells. The fluid flow from the wound to the dressing further assists in the removal of such breakdown products which will otherwise be harmful to the tissues and blood vessels in and around the wound. It was found that the composition in accordance with the invention has both cation and anion exchange properties, so that excessive acidic as well as excessive alkaline exudates can be removed by the dressing.

It is contended that the proved lattice structure of the mineral components of the dressing, the water and the glyoerine it holds, closely resembles the horny layer of normal skin with its lipo-protein content, and that a dressing in accordance with the invention can therefore be used as a substitute for grafted skin to provide 80% fluid control, until the wound has progressed to the healing stage or is ready to have the patients own skin grafted over the wound. The dressing can also be used, as described below and mentioned later on, to prepare wounds for grafting and to cover grafted areas until the graft has healed.

It has been found that the granulation tissue of a wound is ready to receive a graft When the pH of the granulation tissue is 7.4 or higher. The preparation of granulation tissue for grafting presents certain problems. With known methods, when the eschar is removed, an area of raw tissue is exposed from which large fluid and heat losses take place while the surface area is being prepared for grafting, usually by the use of an acidic anti-septic agent. This treatment creates a tissue condition with low pH and which is unfavourable for grafting. pH values of 7.4 and higher are consistently found in the wound surface area, when the soft eschar is removed after treatment by the method and dressing of the invention. Grafting can be undertaken as soon as the remaining dead surface material has been removed.

It is further contended that by controlling the temperature, the venous congestion which occurs in the normal development of a burn wound, is prevented or reversed. In this manner cells and small blood vessels only partially damaged can be saved, and healing is greatly accelerated.

Infection is largely controlled by providing the tissues with blood-borne anti-bacterial substances, and by facilitating the spread and penetration of chemotherapeutic substances such as penicillin introduced into the blood stream.

7 The mineral components of the mixture according to the invention have the mineralogical and base exchange characteristics as set out in the following Tables I and II:

TABLE I.MINERALOGICAL COMPOSITION viously dried at 110 C. and the measurements were made in a constant temperature roorn (20 0.). In all cases, constant readings were obtained after 30 minutes. The

Random mixed-layer clay mineral illite- Hydro- Cal- Kaomontmorilmuscite, linite, Illite, lonite, Quartz, eovlte, per- Component percent percent percent percent percent cent Kaolinite 80-85 ==l South African bentonite 50-55 South African illite -10 2O Elite 80% montmorillonite The particle size distributions of the clays are given below in Table III.

TABLE III Percentage material finer than particle size shown Particle size in microns Kaolinite Illite Beutonite A dry sieve analysis, determined after drying the clays at 110 (3., gave the following results:

TABLE IV Percentage material finer than Particle particle size shown size in I Tyler sieve (mesh) microns Kaolinite Ilhte Bentomte From the water binding capacity values (i.e. the Enslin values) given above in Table II, it will be noted that the Enslin value for a mixture as indicated in that table, is difierent from the value (i.e. 114.6) which would be expected on an average of the parts combined. This indicates that the composition in accordance with the invention displays a synergistic effect, and has properties which are difiFerent from the aggregate of the properties of the various components. Likewise the pH of the mixture as indicated in Table II is different from the expected average value (8.31). The various ingredients of the composition of this invention cannot individually or in aggregate achieve the properties of the composition of this invention unless combined with each other in the manner indicated above.

The water binding capacities (the Enslin values) of the samples were determined by means of an Enslin apparatus. Determinations were made with 0.3 g. clay pre- Enslin values (in cc./ g. clay) give a measure of the total amount of water absorbed and adsorbed.

A further determination, carried out in connection with a mixture the components of which were obtained from diiferent localities, yielded the following results:

TABLE V Water binding capacity (Enslln value) Component pH (00.1100 g. clay) Kaolinite (Sample EV 5) i. 4. 9 I00 Bentonite (Sample 35B) 4. 6 83 Illite (Sample YB) 7. 66 250 Mixture:

4 parts kaolinite. 5 parts bentonite 7. 65 125. 5 3 parts illite It will be apparent to persons skilled in the art that mineral components having substantially the same characteristics as those set out above, may be used in accordance with this invention, regardless of where such components are found. In other words, the terms kaolinite South African bentonite and South African illite should be understood to include mineral components having substantially the same characteristics as set out above, wherever they may be found.

The composition of this invention may be prepared by mixing the mineral ingredients (which have been prepared commercially by the grinding of their larger rock for-mations) with each other in the stated proportions so as to form the mineral mixture. The liquid mixture is then prepared separately, by mixing the water and glycerine in the stated proportions. Thereafter the mineral and liquid mixtures are worked in together in known manner, to form a soft, smooth paste.

Preferably the composition is prepared in the following manner: First the anti-fungal agent is dissolved in a small quantity of the total amount of water, if necessary by boiling. Next the starch is made into a paste with a small quantity of water also taken from the total volume of water, and to this paste is added a further quantity of boiling Water again taken from the total volume of water. The glycerine is added to the remaining volume of cold water and stirred well. Finally the dissolved anti-fungal agent and starch are added to the water-glycerine mixture and stirred well.

The solid components are mixed thoroughly in any suitable mixing apparatus, until a smooth consistency is attained. The solid and liquid components are finally worked in together, to provide a smooth paste.

The composition may be moulded into dressings of about 0.25 to 0.5 inch thick, and in different sizes. The dressing may be provided with one or more backing layers, such as of gauze. In this connection it may be pointed out that, if the backing layers are liquid absorbent, the amount of liquid mixture provided in the composition according to the invention, should be correspondingly increased, so that the amount of liquid in the composition of the final dressing, would be not less than the amount indicated above, notwithstanding the fact that the backing layer or -layers have absorbed a certain amount of liquid.

The dressing may be covered by a sheet of liquid impervious material, such as a cellulosic sheet material, and for-med into a closed package. The finished dressing may then be inserted into a polyethylene and/or aluminum foil packaging, sealed and sterilized, Preferably a high density polyethylene bag is used, which is heat sealed with removal of air during sealing.

A plurality of dressings or poultices, sealed within polyethylene bags, may be packed into a suitable container such as a tin. The tin, properly closed and sealed with autoclaving tape, may then be heated in an autoclave at a temperature of about 250 F. and at lbs. pressure for about 15 minutes, to sterilize the contents. Thereupon the dressings may be removed, cooled, and suitably packed for marketing and use.

The dressing and poultice may conveniently be provided with adhesive attached to the edges thereof, by means of which it may be attached to the injured area being treated. This adhesive may be so arranged as to be left in position while the used dressing is removed and a fresh one is provided.

Comparative tests were carried out at the National Mechanical Engineering Research Institute of the South African Council for Scientific and Industrial Research, on the dressing according to the invention and a conventional type of dressing, in order to obtain information on the heat and mass transfer characteristics of the dressing according to the invention.

(1) DESCRIPTION OF THE DRESSINGS (a) Dressing according to the invention This dressing consisted of a layer of the paste according to the invention, which was held between two layers of gauze to form a pad approximately in. thick. The moisture content of the dressing was approximately 50 percent.

Before use the pads were stored at low temperature in sealed polyethylene bags.

(b) Conventional dressing The conventional type of dressing that was tested consisted of two layers of tulle gras gauze covered by a A in. thick pad of cotton wool and a layer of elastoplast.

(2) TEST RESULTS (a) Thermal conductivity The overall thermal conductivity values were determined from measurements of the heat flux through and the temperature gradient across the respective dressings; the thermal conductivity being given by the equation for the particular thickness of dressing tested, where Q=heat flow rate through the dressing B.t.u./ hr. ft. and t t =inner and outer surface temperature of the dress ing respectively F.).

(i) Dressing according to the invention.-Overall thermal conductivity, k=9.7 B.t.u./ hr. ft. F., for A in. thick dressing without any covering.

(ii) Conventional dressing.-0verall thermal conductivity, k=0.56 B.t.u./hr. ft. F. for the thickness of dress ing described under paragraph 1('b).

(b) Permeance The following o verall permeance values for the dressings were obtained from measurements of the rate of moisture migration through the dressing for certain vapour pressure diflerences between the bottom surface of the dressing and the ambient air. (For the purpose of these tests the vapour pressure below the dressing was controlled by controlling the temperature of a wetted sponge in contact with the dressing.)

The tests were carried out under still-air conditions.

(i) Dressing according to the invention-The following overall permeance values, k were obtained:

k =0.0025 lbs./hr. ft. mm. Hg for the dressing only,

without any covering k =0.002 lbs/hr. ft. mm. Hg for the dressing covered with one layer of crepe bandage k =0.0019 lbs/hr. ft. mm. Hg for the dressing covered with two layers of crepe bandage. (ii) Conventional dressing-Overall permeance value,

k =0.0006 lb./hr. ft. mm. Hg.

(0) The effect of environmental conditions in regard to temperature and humidity, on the total heat loss rate and moisture loss rate from a wetted surface immediately below the dressings The heat loss and moisture loss rates which could be expected to occur from a saturated sponge maintained at a temperature of 95 F., when the sponge is covered with either the dressing of the invention or the conventional type of dressing, were calculated from the results given under 2(a) and (b).

The sponge was assumed to be saturated with a Water plus 5 percent by weight egg-white mixture.

In the case of the dressing of the invention, the dressing was assumed to be covered with two layers of crepe bandage.

The results are summarised in Table A below.

Condition of ambient air Dressing of the invention Heat loss from the surface covered Conventional dressing Heat loss from the surface covered Moisture loss from the surface covered Moisture loss from the surface covered Relative by the dressby the dressby the dressby the dress- Ternp humidity ing (B.t.11./ ing (gms./hr. ing (B.t.u./ ing (gmsJhr. F (percent) hr. ftfl), total it?) hr. ftfl), total it?) 1 1 (3) DISCUSSION Of significance in the results summarised in Table A, is the relatively high heat loss rates which can be expected from a hot wet surface when covered by the dressing of the invention compared to the heat loss rates from a similar surface covered by the conventional type of dressing. Of particular significance is the fact that these relatively high heat loss rates have been achieved in the case of the dressing of the invention without any significant increase in the moisture loss rates from the wetted surface below the dressing. In fact, the moisture loss rates from the wetted surface were invariably reduced when the conventional dressing was replaced by the dressing of the invention. In the case of the conventional type of dressing, the cooling effect of the dressing (on any moist surface below it), can only be improved by increasing the evaporation of moisture from the surface itself. Thus the greater the cooling effect, the greater the moisture loss from the surface.

In the case of the dressing of the invention, a significant proportion of the cooling effect is due to the evaporation of moisture from the dressing itself.

This was evident from changes in the moisture content of the dressing (observed from weight measurements on the dressing), which were found to occur when the permeance values for the dressing were being determined. The rate of weight loss from the dressing was found to be approximately 50' percent of the rate of vapour transmission through the dressing (from the wetted sponge to the outside air), for a normal vapour pressure difference of 35 mms. Hg. (This vapour pressure difference would exist when the temperature of the water below the dressing is 98 F. and the temperature and relative humidity of the surrounding air is 75 and 50% respectively.)

The following are the total rates at which moisture was lost from the surface of the dressing under these conditions. (These values, therefore, include the rate at which water was lost from the surface below the dressing as well as the weight loss rate from the dressing itself):

Lbs/hr. ft. mm. Hg

Dressing only 0.003 8 Dressing covered with one layer of crepe bandage 0.0031

Dressing covered with two layers of crepe bandage 0.003 Dressing covered with one layer of elastoplast 0.0015

The rate of moisture loss from the dressing itself can be determined by subtracting the permeance values given in paragraph 2(b) from the abovementioned values.

In conclusion it may be pointed out that the moisture loss rates referred to in Table A would, in all probability, be less than the indicated values when the dressing is applied to an actual burn wound, the actual amount by which these losses are reduced being dependent to some extent on the overall permeance value of the wound itself.

Such a reduction in moisture loss rate could be considerable in the case of the dressing, bearing in mind that the cooling effect of the dressing results in an appreciable reduction in the tendency for moisture to be released by the Wound.

It is believed that the improved evaporative efiect of the dressing according to the invention, is attained in practice since evaporation takes place from the surface of the dressing. More complete evaporation accordingly occurs, with more effective consequent heat loss. In the conventional dressings, the evaporation takes place from the surface of the wound, and this is less effective, causing less effective heat loss.

In the treatment of burns, the dressing may be applied to a burn immediately after blisters have been opened and loose skin cut away. The dressing should then be removed from 12 to 24 hours later, and thereafter renewed at intervals of between 12 and 24 hours, as deemed necessary. Before applying a dressing, it may advantageously be cooled to a suitable temperature, so as to decrease the temperature of the injury to which it is to be applied. The cooled dressing will then in practice automatically and slowly heat up again to a temperature in the region of the normal body temperature of the person being treated, and it will maintain this temperature by reason of a limited evaporation through the dressing of body fluids. The advantages of this controlled cooling and heating effect have been indicated above.

It was proved experimentally that the dressing according to the invention has a controlled evaporation, namely of about 20% of the normal zfluid loss by evaporation through the skin, and this property ensures that the injured area is kept at a constant temperature not too high above the normal body temperature. In order to maintain this steady rate of evaporation, fluids are drawn from the injured area, which fluids contain products of autolysis. It will be evident that the removal of these endproducts of the cell breakdown process, is desirable. The exudate drawn to the surface of the injured area, may be removed by swabbing when the dressing is renewed.

Experimental work was carried out with the composition according to the invention, and the results of this work will be given below:

Copper-'constantan thermocouples and a potensiometer were used to measure the various temperatures of the injured area in each case, as well as of an uninjured portion of the skin, prior to application of the dressing, and also after the dressing has been applied. The accuracy of the temperature measurements was of the order of 0.l F.

Temperatures were taken as follows:

This was done by fixing the thermocouple onto the skin by means of elastoplast and then covering it with an inch layer of cottonwool.

FIRST TEST A patient obtained a burn wound on the lower part of the abdomen. The following Table VI indicates the temperatures at different positions on the wound and on uninjured skin.

TABLE VI Position: Temperature, F. 1 94.5 2 95.1 3 95.9 4 (uninjured skin) 91.1

These temperature measurements show that the temperature of the damaged skin was much higher than that of the uninjured skin.

Immediately after application of a dressing in accordance with the invention, the surface temperature of the wound decreased to about 10 F. below that of the healthy skin. After about 1 /2 hours, the condition became steadier and an equilibrium was reached, at which the temperature of the wound remained about 1 F. below that of the uninjured skin.

After the dressing had been changed, the process repeated itself. The wound showed no free moisture on the surface.

SECOND TEST The patient received burn wounds on the abdomen. The following table indicates the temperature on the wound and on an uninjured portion of the skin, prior to treatment.

13 TABLE VII Position: Temperature, F. l 97.1 2 93.1 3 92.1 4 94.2 92.8 6 (uninjured skin) 90.5

A dressing in accordance with the invention was applied to the burned area. After about an hour the temperature of the wound remained about 25 F. below that of the normal skin, and the heat flow was about 2.8 gr. oak/100 cmF/sec. from the wound surface to the outside.

THIRD TEST The patient received burn wounds on the arm from the shoulder to the fingers. The following Table VIII, indicates the temperatures taken on the injured area prior to treatment.

TABLE VIII Position: Temperature, F. 1 83.9 2 83.5 3 84.8 4 87.5 5 81.9 6 82.4 7 80.5 8 79.6 9 78.9 10 73.3 11 (uninjured skin) 94.4

The arm seemed moist and the arms temperature was lower than that of the uninjured skin. (This was probably due to the fact that the arm was exposed whereas the rest of the body was covered.) The upper portion of the arm (positions 1 to 4) had a higher temperature than the portion below the elbow (positions 5 to 10).

A dressing in accordance with the invention was applied to the whole arm, and the portion between the elbow and the wrist was covered with a single layer of plastic material (polyethylene). The plastic covering acted as a vapour barrier on the outer surface of the dressing.

Originally the temperature of the burned area was lower than that of the uninjured skin (probably because the arm was exposed whereas the rest of the body was covered) and this condition remained the same throughout the tests. However, the temperature of the portion of the arm that had been covered with the plastic material, was about l.5 F. higher than the temperature of that section of the arm that had only the dressing of the invention on it, in spite of the fact that the temperature of the upper arm was initially higher. Condensation of water vapour took place against the plastic layer, whereas the arm itself also seemed wet after the dressing had been removed. The average heat flow through the dressing that had been covered with the plastic material, was lower than the heat flow through the rest of the dressing.

The condition was now reversed, and the plastic material was applied onto the dressing covering the upper arm. The heat flow through that portion of the dressing covering the upper arm immediately decreased, whereas the heat flow from the wound to the surface of the dressing of the lower arm increased.

After having treated, by way of experiment, more than 200 clinical cases, the following detailed description of the reactions obtained in the majority of cases may be given:

As an example a burn wound which includes all three grades of depth of injury (i.e. destruction of the epidermis with minimal capillary damage, second degree injury extending to below the deeper capillary plexus, and full thickness injury where full thickness skin loss is present) will be described. The dressing is applied to cover the whole area, and when removed 24 hours later, it does not adhere to the wound by reason of the presence of a thin serous exudate. This is gently swabbed or rinsed away, and another dressing is applied. With each 24 hour removal, the exudate increases and becomes thicker, until by 72 to 96 hours it occurs in the form of a soft pellicle over the least deep area only. This pellicle is painlessly pulled away from the wound, and the wound shows a pink surface where epithelization is in progress. In another two or three days time, this part of the wound is healed, and it can be painted with a very dilute solution of a drying agent.

The dressings are now made smaller for the two deeper portions of the burn area, which have continued to produce a fairly thick exudate. By the eighth to the tenth day, exudation automatically ceases over the second degree injured area, and epithelization is completed over those parts.

The dressing is again made smaller to cover only the full thickness injured area, which has continued to show a thinner serous exudate, and which has remained fairly soft and pliable when treated with light pressure. By the tenth to the twelfth day, a remarkable phenomenon is observed. The full thickness dead skin loosens sufliciently at the edges to allow it to be pulled away in sections from the underlying clean soft granulations. The dressing is continued daily until all the slough is cleared, when the surface is immediately ready for grafting. When the grafts have been applied, the same dressing may be used over these and it may be secured with two windings of gauze. A protective cover which exerts gentle pressure is thus provided. After three days, the dressing may be removed when it yvill be found that the graft backing gauze now adheres to the dressing, and the grafts are firmly attached to the receiving area.

As described above, the dressing according to the invention, has the effect of permitting a controlled degree of fluid evaporation, which has the result of concentrating the exudate of the wound area since a proportion of the water portion of the exudate also evaporates. This concentration discourages bacterial growth, so that the dressing has a bacteriostatic effect. Furthermore, the gelatinous nature of the concentrated exudate prevents the dressing from adhering to the wound surface.

Experiments were carried out with batches of the composition inoculated with staphylococci and coliform bacilli. Very few colonies of staphylococci could be isolated after only four hours, while decreasing numbers of coliform colonies were found on each successive day for three days.

An additional feature of the dressing is that, due to the controlled degree of evaporation which it permits, the dressing in effect sets up a column above the wound area, which by osmotic action draws fluid and cellular debris, including bacteria and their toxins, to the surface of the wound. Removal can now be brought about readily.

Whilst the use in practice of the composition of this invention has been described above with reference to the treatment of burn wounds, it will be apparent to persons skilled in the art that the composition of this invention may also be used in other treatments, such as the treatment of old infected granular burn surfaces which cannot heal and which will not take a graft, infected surgical or traumatic wounds, septic skin conditions, varicose and decubitus ulcers, etc.

The advantages which can be obtained by the use of the composition of this invention, may be summarised as follows:

(1) It can be applied in the first instance by any lay person.

(2) It protects the wound area immediately from physical damage.

(3) It has a splinting efiect to limbs, but it can be applied so as to allow for some movement of the joints.

(4) It can be moulded to conform to any part of the body, such as the fingers or toes.

(5) It relieves pain.

(6) It does not stick to the wound and may be removed and reapplied with little or no discomfort. It allows for daily inspection of the wound.

(7) It cools the underlying tissues by being applied at to 20 C.

(8) It continues this cooling by drawing fluid from the wound, and allowing it to evaporate from the surface of the composition, as a result of its porosity.

(9) The cooling has a beneficial effect upon the blood capillaries in the skin, helping to maintain circulation essential to skin rebuilding.

(10) The fluid drawin geifect also causes autolysis products, which are detrimental to the blood vesels, to be drawn to the surface of the wound, and to be absorbed by the dressing, thus reducing the harmful effect of these substances.

(l1) Usual disagreeable odours are prevented by the same absorption process.

(12) It reduces excess fluid loss from the injured area by maintaining circulation in blood vessels and thus facilitating reabsorption of fluid, and also by controlling the evaporation of fluid from the dressing surface.

(13) It controls infection by absorbing bacteria and/or their toxins, and it prevents bacteria from entering the wound by reason of the movement of fluid towards the surface.

(14) It can be applied to any part of the body.

(15) It minimises the necessity of grafting operation, and where grafting operations are still necessary, they can be done much sooner than in the case of present treatment.

(16) It reduces contractures and scar tissue. It has been stated that scar tissue is produced by fibrosis of the blood vessels through irritation by particles of hairs from the follicles and keratinised epithelical cells from the sweat ducts. The composition withdraws these particles into the exudate, and so prevents irritation and consequent scar tissue formation.

(17) It can be stored in small spaces.

(18) When full thickness debridement it carried out and insufficient autograft material is available, the part grafted and the adjoining non-grafted area can be covered with the same dressing and left in position for three days. The non-grafted area can be covered in this way for weeks, with periodical changes, thus taking the place of donor skin.

I claim:

1. A dressing for treating inflammation of skin tissue which comprises a backing layer to which has been applied a paste comprised of a mixture of an equal weight of mineral components (a) a mixture of liquid components (b), said mixture of mineral components (a) comprising (i) 25 to 38% by weight of South African bentonite having a mineralogical composition by weight of about 50% to 55% kaolinite, about 10 to 15% of illite, about 30 to 35% of quartz and about 2 to 3% by weight of calcite, (ii) 30 to 50 by weight of kaolinite mineral having a mineralogical composition by weight of about 80 to 85% of kaolinite, about 10% of quartz and about 5 to 10% of hydromuscovite, (iii) 18 to 30% by weight of South African illite having a mineralogical composition by weight of about 5 to 10% of kaolinite,

about 50% of illite, about 25% of random mixed-layer clay mineral consisting essentially of by weight of illite and 20% by weight of montmorillonite, and about 20% of quartz, said mixture of liquid components (b) comprising 8 to 10 parts by weight of water and 4 to 2 parts by weight of glycerine.

2. A paste composition for treating inflammation of skin tissue which comprises an equal weight of a mixture of mineral components (a) and a mixture of liquid components (b), said mixture of mineral components (a) comprising (i) 25 to 38% by weight of South African bentonite having a mineralogical composition by weight of about 50% to 55% kaolinite, about 10 to 15% of illite, about 30 to 35% of quartz and about 2 to 3% by weight of calcite, (ii) 30 to 50% by weight of a kaolinite mineral having a mineralogical composition by Weight of about 80 to of kaolinite, about 10% of quartz and about 5 to 10% of hydromuscovite, (iii) 18 to 30% by weight of South African illite having a mineralogical composition by weight of about 5 to 10% of kaolinite, about 50% of illite, about 25% of random mixed-layer clay mineral consisting esentially of 80% by weight of illite and 20% by weight of montmorillonite, and about 20% of quartz, said mixture of liquid components (b) comprising 8 to 10 parts by weight of Water and 4 to 2 parts by weight of glycerine.

3. A method of preparing a dressing for treating inflammation of skin tissue which comprises the steps of (a) rendering an equal weight of a mixture of mineral components (a) into a paste composition by addition of a mixture of liquid components (b) said mixture of mineral components (a) comprising (i) 25 to 30% by weight of South African bentonite having a mineralogical composition by weight of about 50% to 55% kaolinite, about 10 to 15% of illite, about 30 to 35% of quartz and about '2 to 3% by weight of calcite, (ii) 30 to 50% by weight of kaolinite mineral having a mineralogical composition by weight of about 80 to 85% of kaolinite, about 10% of quartz and about 5 to 10% of hydromuscovite (iii) 18 to 30% by weight of South African illite having a mineralogical composition by Weight of about 5 to 10% of kaolinite, about 50% of illite, about 25% of random mixed-layer clay mineral consisting essentially of 80% by weight of illite and 20% by weight of montmorillonite, and about 20% of quartz, said mixture of liquid components (b) comprising 8 to 10 parts by weight and 4 to 2 parts by weight of glycerine, and (b) applying the paste composition to a backing layer of gauze.

References Cited UNITED STATES PATENTS 2,523,316 9/1950 McClenahan et al. 424-308 X 3,339,546 9/1967 Chen 42428 X 3,348,905 10/1967 Reveley 424-28 X OTHER REFERENCES Pharmaceutical Formulas, 1955, pp. 5-0, 51, 203, 273, 281, 842, 843, 865, 927.

The Condensed Chemical Dictionary, 1961, pp. 282.

ALBERT T. MEYERS, Primary Examiner D. R. ORE, Assistant Examiner US. Cl. XJR.

l281, 154; 424Dig. 13, 154 

